Calculate the fare for a mobility service provider based on distance between a pickup and drop location (Node.js)

In this use case, the user provides his pickup and drop location to a mobility service provider to get the calculated fare

Code snippets

Client calls the BAP server to trigger search:

    router.post("/mobility/calculate_fare", calculateFare);

    async function calculateFare({ body }, res) {
        try {
            //  .. Validate the client request before below function
            await generateSearchRequest(body)
        } catch (error) {
            res.status(500).send(httpResponse("NACK", error));
        }
    };

BAP server generates the protocol request body

    // Code to generate the protocol request body i.e. function generateSearchRequest() specified above
    async function generateSearchRequest(clientRequestBody) {
/*
Example Request JSON :
{
    "context": {
        "domain": "nic2004:60221",
        "country": "IND",
        "city": "std:080",
        "action": "search",
        "core_version": "0.9.1",
        "bap_id": "https://mock_bap.com/",
        "bap_uri": "https://mock_bap.com/beckn/",
        "transaction_id": "1209849124",
        "message_id": "12341242342",
        "timestamp": "2021-03-23T10:00:40.065Z"
    },
    "message": {
        "intent" : {
            "fulfillment": {
                "start" : {
                    "location" : {
                        "gps" : "12.9349377,77.6055586"
                    }
                },
                "end" : {
                    "location" : {
                        "gps" : "12.4535445,77.9283792"
                    }
                }
            }
        }
    }
}
*/
        //The below code generates the above example JSON.
        const transactionId = _.get(body, "transactionId");
        // Returns the Context including MessageId
        const context = createContext(transactionId);
        const searchRequestBody = {
            context,
            message:  {
                intent: {
                    fulfillment: {
                        // Construct from the request
                    },
                }
            }
        };
        //call protocol search
        const response = await callSearch(searchRequestBody);
        res
        .status(200)
        .send({ ...response.data, messageId: context["message_id"] });
    }

BAP server calls protocol search to the network

   async function callSearch(searchRequestBody) {
        // It lookups the registry for BG OR BPP
        let uri = lookup();
        // Construct Header
        const headers = constructAuthHeader(); // Auth Header with digital Signature
        return axios({ url: `${uri}/mobility/search`, method: "POST", data: request, headers});
    }

BAP receives protocol on_search

/*
Example Response JSON:
{
    "context": {
        "domain": "nic2004:60221",
        "country": "IND",
        "city": "std:080",
        "action": "on_search",
        "core_version": "0.9.1",
        "bap_id": "https://mock_bap.com/",
        "bap_uri": "https://mock_bap.com/beckn/",
        "bpp_id": "https://mock_bpp.com/",
        "bpp_uri": "https://mock_bpp.com/beckn/",
        "transaction_id": "1209849124",
        "message_id": "12341242343",
        "timestamp": "2021-03-23T10:00:40.065Z"
    },
    "message": {
        "catalog": {
            "bpp/descriptor": {
                "name": "Mock BPP"
            },
            "bpp/providers": [
                {
                    "id": "yellow-cabs",
                    "descriptor" : {
                        "name": "Yellow Cabs"
                    },
                    "locations": [
                        {
                            "id": "closest-suv-spot",
                            "gps": "12.9349377,77.6055586"
                        },
                        {
                            "id": "closest-sedan-spot",
                            "gps": "12.9349377,77.6055586"
                        },
                        {
                            "id": "closest-sedan-outstation",
                            "gps": "12.9349377,77.6055586"
                        }
                    ],
                    "categories": [
                        {
                            "id": "spot_booking",
                            "descriptor": {
                                "name": "Spot booking"
                            }
                        },
                        {
                            "id": "outstation",
                            "descriptor": {
                                "name": "Outstation"
                            }
                        }
                    ],
                    "items": [
                        {
                            "id": "sedan_spot",
                            "descriptor" : {
                                "name" : "4 seater Sedan",
                                "images" : [
                                    "https://mock_bpp.com/images/sedan.jpg"
                                ]
                            },
                            "category_id": "spot_booking",
                            "location_id": "closest-sedan-spot",
                            "price" : {
                                "currency": "INR",
                                "value": "170"
                            },
                            "time": {
                                "label": "ETA",
                                "duration": "P14M"
                            }
                            "matched": true
                        },
                        {
                            "id": "suv_spot",
                            "descriptor" : {
                                "name" : "6 seater SUV ",
                                "images" : [
                                    "https://mock_bpp.com/images/suv.jpg"
                                ]
                            },
                            "category_id": "spot_booking",
                            "location_id": "closest-suv-spot",
                            "price" : {
                                "currency": "INR",
                                "value": "290"
                            },
                            "time": {
                                "label": "ETA",
                                "duration": "P12M"
                            }
                            "matched": true
                        },
                        {
                            "id": "sedan_outstation",
                            "descriptor" : {
                                "name" : "4 Seater Sedan",
                                "images" : [
                                    "https://mock_bpp.com/images/sedan-out.jpg"
                                ]
                            },
                            "category_id": "outstation",
                            "location_id": "closest-sedan-outstation",
                            "price" : {
                                "currency": "INR",
                                "value": "570"
                            },
                            "time": {
                                "label": "ETA",
                                "duration": "P17M"
                            }
                            "matched": true
                        },
                    ]
                },
                {
                    "id": "cabs-4-all",
                    "descriptor": {
                        "name": "Cabs 4 All"
                    },
                    "locations": [
                        {
                            "id": "closest-sedan",
                            "gps": "12.9349377,77.6055586"
                        }
                    ],
                    "categories": [
                        {
                            "id": "rental",
                            "descriptor": {
                                "name": "Rental"
                            }
                        }
                    ],
                    "items": [
                        {
                            "id": "sedan_rental",
                            "descriptor" : {
                                "name" : "Sedan 5 hours",
                                "images" : [
                                    "https://mock_bpp.com/images/sedan_rental.jpg"
                                ]
                            },
                            "category_id": "rental",
                            "location_id": "closest-sedan",
                            "price" : {
                                "currency": "INR",
                                "value": "200"
                            },
                            "time": {
                                "label": "ETA",
                                "duration": "P12M"
                            }
                            "matched": true
                        }
                    ]
                }
            ]
        }
    }
}
*/
    // Auth middleware authenticates the digital signature of the incoming request
    router.post("/mobility/on_search", auth, onSearch);
    async function onSearch({ body }, res) {
        // Save the response to Database
        await saveToDb(body);
    };

Client polls BAP to get the on_search results

    // Endpoint for the client to poll the search data based on the message id
    async function getMessageById(req) {
        try {
            const messageId = _.get(req, "messageId");
            // Get the data using message Id
            const response = await getData(messageId);
            res.status(200).send(httpResponse('ACK', "", response));
        } catch(error) {
            res.status(500).send(httpResponse("NACK", error));
        }
    };